To expand what Steve said a little bit:
If one person tests a Brand XYZ in a certain circuit it might sound superior to Brand ZYX. In another circuit it might be exactly the opposite.
If you take one batch of these XYZ tubes and put them into the same circuit each tube will sound different. Even the best brand tubes will have a bunch of sh*tty tubes amongst them, even worse, some are crapping out very early. That´s how it has been since the beginning and it will never change. This has to do with the manufacturing process and quality control. There are one thing to consider when putting a tube in a circuit: checking if it´s microphonic (spell?). But that´s it. Turn your amp on and snip with a finger (not touching anything except the glass of the tube - otherwise you might regret it or your family might regret it) against the tube. If you hear a ringing sound it´s bad. You will always hear something but the better the tube the shorter the sound is. Do it with a few tubes and you will get an idea of what good and bad is.
Since I´m building tubegear I did quite a lot of listening tests: brands, types, series, old/new, whatever. But what I do is proaudio studiogear where quality is highly required. For this application I found a way (my way) how to deal with it. In a bass- or guitaramp where distortion is wanted I personally give a flying f*** on the tubes. Put them in and turn it up. If it sounds right it is right. If you have to complain about the sound swap tubes or better use a different amp because the circuit itself adds way more to the sound than one particular tube.
If you think this particular tube is essentially important to your basssound then you´d better not play in a band where other musicians disturb your perfect sound perception. But that´s just my humble opinion. YMMV